The present invention relates to label converting and application, and more particularly to an apparatus and method for converting label base stock to a roll of releasably backed labels.
Self-adhesive or pressure-sensitive labels are used in a wide variety of applications for labeling bottles, jars, and other containers and articles. The label application equipment operates at high speeds resulting in thousands of labeled articles per hour. The label manufacture and application typically fall into two broad techniques, depending on whether the label stock is converted into labels during manufacture of the labels (and therefore well prior to application) or as part of the application process.
In the first technique, the labels are individually formed on a continuous web (also known as a release liner) prior to their use in the application equipment. In this case, the release liner is pulled through the machine, and the labels are transferred from the release liner to the articles to be labeled. The application equipment draws the release liner about a peel edge adjacent the article to be labeled. Because the label is stiffer than the release liner, the label continues in a straight line past the peel edge and onto the article. This first technique involves sophisticated label manufacture, but straightforward label application. Consequently, the application equipment and processes are relatively simple, inexpensive, and reliable.
In the second technique, the labels are cut from a continuous web of label stock at or adjacent the application equipment. In this case, the face web is severed into discrete labels. The cut labels are applied to the articles as quickly as they are cut. The second technique involves straightforward label manufacture but sophisticated label application. Consequently, the application equipment is less simple, more expensive, and less reliable.
In this second technique, the labels can be cut either before or after the face web is separated from the liner. "Butt cut" is a term describing a label cut that severs the web transversely from edge to edge to form individual labels from the face web without the disadvantage of creating a waste label skeleton or matrix associated with "die cuts," which are discussed below. If cutting occurs before the face web is separated from the release web, a butt cut knife blade cuts deeply enough to sever both the face web and pressure sensitive adhesive layer on its back--without penetrating the release liner. This requires precision cutting that is difficult to maintain in actual use conditions. If the cut is too deep, then the backing liner may be weakened to the point that the backing liner breaks as it is pulled through automated label application machinery. This causes expensive downtime and wasted material. If the butt cut is not deep enough, then the label will not cleanly separate during application. Further, the operator must randomly inspect the labels after the cuts have been made to determine whether the cut is deep enough.
Alternatively, the face web may be cut when it is not attached to the release liner--either because the equipment separates the face web from the release liner or because the label stock is "linerless" (meaning that it never included a liner). An example of this approach is illustrated in International Patent Application No. WO 90/05089 entitled "Improvements Relating to the Application of Labels to Articles" published May 17, 1990, which describes a label applicator that makes and applies butt cut labels without the use of a backing liner. The vacuum chamber provides the suction to hold the butt cut label until the conveyor belt transfers it to the applicator station, where a roller and belt apply the label to the article. (International Application at pages 9-11.) Because the butt cut label lacks a backing liner, this apparatus requires an elaborate means--comprising parallel conveying belts supported by guide rollers and channels with a vacuum chamber between the guide rollers--to hold the butt cut label during application. (International Application, FIG. 2.)
In contrast to a butt cut, a "die cut" is a label cut made by a patterned cutting blade that severs the web to form a label having a desired configuration, leaving a skeleton or matrix waste of face web material. If the base stock does not include a backing liner, then the die cut skeletal waste of the face web provides the means for pulling the face web through the automated labeling equipment. See, for example, Canadian Patent 1,248,412 entitled "Self Adhesive Labels and the Manufacture Thereof" issued Jan. 10, 1989 (page 16 and FIG. 7).
The previously cited International Patent Application No. WO 90/05089 at page 2 also discloses the application of die cut labels to articles. A cutting drum and anvil cooperate to die cut labels from a continuously fed base stock having a pressure sensitive adhesive coating on one side. Each label, after being cut from the web, is held to the anvil by a vacuum until the label reaches the application station, where the label is released and applied to the article. The face web is pulled through the labeling machine by the skeletal face web waste formed by the die cut.